298 The Rev. W. Buckland on the Plastic Clay Formation. 



at Newhaven and Chimting Castle, appear again on the opposite 

 shores of France in the same relative position. 



I am indebted to the kindness of M. Brongniart for the following 

 section near Dieppe, which forms a valuable link connecting the 

 formations above the chalk in France with those of the same era in 

 the south of England. He has observed the following strata in the 

 perpendicular cliff under the light-house of St. Margaret, on the west 

 of Dieppe, counting upwards from the lowest stratum : 



1. Chalk. 



2. Sand and sandstone in thick beds containing concretions of the 

 same substance. 



3. Strata of plastic clay, impure and containing lignite much 

 charged with iron pyrites, also oysters and cerithia, both in beds and 

 irregularly disseminated. 



4. Alluvium. 



These strata M. Brongniart considers as identical with beds of the 

 plastic clay formation in many other parts of France, particularly at 

 Marly, and in the Soissonnois, where the same organic remains oc- 

 cupy strata similarly disposed and identical with those near Dieppe. 



I shall add a few more circumstances of resemblance in the French 

 and English formations of plastic clay. 



It is noted by M. M. Cuvier and Brongniart, that in the basin of 

 Paris the sand between the chalk and plastic clay, though very pure, 

 is often coloured red or bluish grey. In the latter state it occurs at 

 Woolwich, Lewisham, and Newhaven. We have already (p. 280.) 

 stated the analogy which the Reading oyster bed bears to the brec- 

 ciated bed next above the chalk at Meudon. Of the plastic clay it 

 is also stated by the same authority that it often consists of two beds 

 separated from each other by a stratum of sand. The lowest of these 

 two being properly the pure plastic clay, while the upper is coarse, 



